(1) Field of the Invention
This invention relates to comparators used in analog to digital converters and to analog to digital converters using the comparators. The bisection comparator of this invention uses three inverting amplifiers. No auto zero phase is used in the bisection comparator. There is no sample/hold in the bisection comparator and capacitors are not used.
(2) Description of Related Art
An auto zero comparators are the most widely used comparators in CMOS Flash analog to digital converters and Two Step analog to digital converters. U.S. Pat. No. 4,903,028 to Fukushima describes a two step analog to digital converter using a plurality of resistors. U.S. Pat. No. 5,298,814 to Caruso describes comparators using inverting amplifiers with an auto zero phase. U.S. Pat. No. 4,733,217 to Dingwall describes two step analog to digital converters.
Conventional analog to digital converters use sample and hold circuits which require capacitors. These capacitors are large and require large integrated circuit elements. Conventional analog to digital converters using comparators with inverting amplifiers use an auto zero phase to bias the inverting amplifiers at the threshold voltage where the current and the power dissipation in the inverting amplifier is greatest. The bisection comparator of this invention does not use either an auto zero phase or a capacitor for a sample hold circuit. The bisection comparator of this invention has less power dissipation and is smaller than conventional comparators.